<!DOCTYPE html>
<html lang="en">
<head>
	<meta charset="UTF-8">
	<title>制作导航</title>
	<style type="text/css">
		.box{
			width: 800px;
			height: 40px;
			background: pink;
			margin: 20px auto;
		    
		}
		.box ul li{
			margin: 0px;
			padding: 0px;
			list-style: none;
			float: left;
			height: 40px;
         /* 把浮动写在这里*/
         margin:20px/40px ;
     

		}
		.box ul li a{
			text-decoration: none;
		}
		a:hover{
			background:#BBBBBB;
		}
	</style>
</head>
<body>
	<div class="box">
		<ul>
		
			<li><a href="#">百度一下</a></li>
			<li><a href="#">贴吧</a></li>
			<li><a href="#">知道</a></li>
			<li><a href="#">文库</a></li>
		</ul>
	</div>
</body>
</html>